When functioning properly, the human heart maintains its own intrinsic rhythm. Its sinoatrial node generates intrinsic electrical cardiac signals that depolarize the atria, causing atrial heart contractions. Its atrioventricular node then passes the intrinsic cardiac signal to depolarize the ventricles, causing ventricular heart contractions. These intrinsic cardiac signals can be sensed on a surface electrocardiogram (i.e., a “surface ECG signal”) obtained from electrodes placed on the patient's skin, or from electrodes implanted within the patient's body (i.e., an “electrogram signal”). The surface ECG and electrogram waveforms, for example, include artifacts associated with atrial depolarizations (“P-waves”) and those associated with ventricular depolarizations (“QRS complexes”).
A normal heart is capable of pumping adequate blood throughout the body's circulatory system. However, some people have irregular cardiac rhythms, referred to as cardiac arrhythmias. Moreover, some patients have poor spatial coordination of heart contractions. In either case, diminished blood circulation may result. For such patients, a cardiac rhythm management system may be used to improve the rhythm and/or spatial coordination of heart contractions. Such systems often include a cardiac rhythm management device that is implanted in the patient to deliver therapy to the heart.
Cardiac rhythm management systems include, among other things, pacemakers, also referred to as pacers. Pacers deliver timed sequences of low energy electrical stimuli, called pace pulses, to the heart, such as via an intravascular lead wire or catheter (referred to as a “lead”) having one or more electrodes disposed in or about the heart. Heart contractions are initiated in response to such pace pulses (this is referred to as “capturing” the heart). By properly timing the delivery of pace pulses, the heart can be induced to contract in proper rhythm, greatly improving its efficiency as a pump. Pacers are often used to treat patients with bradyarrhythmias, that is, hearts that beat too slowly, or irregularly. Such pacers may also coordinate atrial and ventricular contractions to improve pumping efficiency.
Cardiac rhythm management systems also include cardiac resynchronization therapy (CRT) devices for coordinating the spatial nature of heart depolarizations for improving pumping efficiency. For example, a CRT device may deliver appropriately timed pace pulses to different locations of the same heart chamber to better coordinate the contraction of that heart chamber, or the CRT device may deliver appropriately timed pace pulses to different heart chambers to improve the manner in which these different heart chambers contract together.
Cardiac rhythm management systems also include defibrillators that are capable of delivering higher energy electrical stimuli to the heart. Such defibrillators include cardioverters, which typically synchronize the delivery of such stimuli to sensed intrinsic heart activity signals. Defibrillators are often used to treat patients with tachyarrhythmias, that is, hearts that beat too quickly. Such too-fast heart rhythms also cause diminished blood circulation because the heart isn't allowed sufficient time to fill with blood before contracting to expel the blood. Such pumping by the heart is inefficient. A defibrillator is capable of delivering a high energy electrical stimulus that is sometimes referred to as a defibrillation countershock, also referred to simply as a “shock.” The shock interrupts the tachyarrhythmia, allowing the heart to reestablish a normal rhythm for the efficient pumping of blood. In addition to pacers, CRT devices, and defibrillators, cardiac rhythm management systems also include devices that combine these functions, as well as monitors, drug delivery devices, and any other implantable or external systems or devices for diagnosing or treating the heart. Cardiac rhythm management systems often include external local or remote user interfaces (sometimes referred to as “programmers” or “patient management systems”) for programming parameters (constraints) of an implantable cardiac rhythm management device or receiving data telemetered from the implantable cardiac rhythm management device.
One problem faced by cardiac rhythm management systems and other Personal Programmable Medical Devices (“PPMD”) is in using an external user interface to program its parameters, such as to tailor the therapy delivered to the needs of the particular subject being treated by that device. For example, programmable implantable cardiac rhythm management devices often make use of a plethora of programmable parameters. Moreover, such programmable parameters may interact with each other. For example, programming a first parameter to a particular value may limit the range of particular values to which a second parameter may be programmed. Because of this interaction between different programmable parameters, a complex set of constraints typically governs how the set of parameters may be programmed. Consequently, a physician faces a daunting task in programming the whole set of parameters to self-consistent values. Moreover, as new therapies are developed (e.g., congestive heart failure therapies that treat both left and right sides of the heart), more parameters and more interactions between parameters are inevitable, further complicating the task of programming a complete set of parameters to allowable values. In addition, new implantable, programmable medical device systems for applications other than the heart itself are continuously developed, ever increasing the number of potential parameters and interactions between parameters. Often, programming one parameter or a set of parameters to a particular value results in invalid results when combined with other interdependent parameter values, causing a complex trial and error analysis for the user. One method of reducing the difficulty of programming parameter values is through establishing manufacturer's default values. This method, however, does not allow the flexibility needed by the physician to specifically tailor a treatment to a particular patient.
Tailoring treatment for a particular patient typically requires programming one or more parameters of the device away from the manufacturer's default values. The current method used to program a PPMD is very inefficient when a large number of parameter interdependencies exist. Often, complex parameter interaction constraints govern interdependencies between parameters. Such parameter interaction constraints are typically defined by the PPMD manufacturer.
To program one or more parameters away from the manufacturer defaults, a user-specified set of parameter values is obtained from the user, and automatically compared to the parameter interaction constraints to determine whether a constraint violation has occurred. If no constraint violation exists, the user-specified parameters are accepted into the PPMD. However, if a constraint violation does exist, the user may be advised of one or more of the violation's existence, the reason for the violation, or a description of the nature of the constraint rule. However, it is then typically left entirely up to the user to modify the existing set of parameter values to try to remove the violation without inadvertently triggering another violation. In fact, this can be a complex and daunting task.
While it may sometimes be possible for the user to achieve a violation-free second set of parameters in a short number of iterations and an acceptable amount of time, the existence of more parameters will typically increase the number of iterations needed and the difficulty of achieving any acceptable set of violation-free parameter values. This decreases the productivity of the user (in most cases a physician), and increases the possibility of errors.